Foamed material filled with inner material

Details Foamed material filled with inner material Foamed material filled with inner material

2002-02-12

2003-10-21

Therkorn, Ernest G. (Department: 1723)

Liquid purification or separation

With means to add treating material

Chromatography

C210S502100, C210S635000, C210S656000, C502S401000

Reexamination Certificate

active

06635174

ABSTRACT:

REFERENCE TO RELATED APPLICATIONS
This application is a 371 of PCT/EP00/04105 filed May 8, 2000.
BACKGROUND TECHNOLOGY
In chromatography a flow of liquid containing components to be removed from the liquid is allowed to pass through a separation medium. The components typically differ in their interactions with the separation medium resulting in a differential retention. The components will become at least partially separated from each other. The efficiency of a separation medium will, among others, depend on the surface area available for the solute.
There is a general desire to increase the available surface area in direct contact with the through flowing liquid. In case the liquid is aqueous and the separation media based on a hydrophobic material, a hydrophilic coating has been provided, for instance. Various thicknesses have been suggested from monomolecular and thicker layers permitting through flow in the centre of the pores (EP 221,046 and WO 9719347, respectively) up to filling the through flow pores completely (EP 288,310).
By the term “through flowing liquid” is meant that the liquid provides convective mass transport. Surfaces accessible by the through flowing liquid are therefore called “convective surfaces”. Analogously pores/pore systems accessible by the through flowing liquid are called “convective pore systems” (for instance pore system 1 described below). The pore sizes of convective pore systems are typically ≧0.1 &mgr;m, such as ≧0.5 &mgr;m, by which is meant that a sphere ≧0.1 &mgr;m respective ≧0.5 &mgr;m in diameter is able to pass through. In case the media is in form of beads packed to a bed, the ratio between convective pore sizes and the diameter of the beads typically is in the interval 0.01-0.3, with preference for 0.05-0.2. Pores having sizes ≧0.1 &mgr;m, such as ≧0.5 &mgr;m, are often called macropores.
Separation media may also have pore systems that are only accessible by diffusion of liquid and/or of components present in the liquid (diffusive mass transport) (“diffusive pore system”, for instance pore system 2 as described below when being microporous). Diffusive pore systems are characterized in having openings into the convective pore system, which are not large enough for the liquid flow to pass through. These openings of pore system 2 are typically such that only spheres with diameters ≦0.5 &mgr;m, such as ≦0.1 &mgr;m, can pass through. Pores having sizes ≦0.5 &mgr;m, such as ≦0.1 &mgr;m, are often called micropores.
The figures for pore sizes given in the context of the present invention refer to values obtained by SEM or ESEM (scanning electron microscopy and environmental scanninmg electron microscopy, respectively) and/or by SEC (size exclusion chromatography) utilising polystyrenes and dextrans, for instance. See Hagel, “Pore Size Distribution” in “Aqueous Size-Exclusion Chromatography” Elsevier Science Publisher B.V., Amsterdam, The Netherlands (1988) 119-155.
THE OBJECTS OF THE INVENTION
A first object is to increase the total capacity of macroporous matrices.
A second object is to increase the break through capacity of matrices comprising macropores filled up with separation media.
Total capacity and break through capacity refer to the ability of the matrices to interact with a substance present in a liquid that flows through the matrices. The interaction may relate to affinity binding between the substance and a ligand structure having affinity for the substance and being present on the support matrix. The interaction may also be a sterically restricted permeation due to the size and shape of the substance.
THE INVENTION
It has now been recognized that these objects can be met in case the macropores of a base matrix comprise an interior material that leaves a continuous free volume between the interior material and the inner walls of the macropores.
A first aspect of the invention is a support matrix comprising a) a base matrix, preferably polymeric, with macropores (pore system 1) and b) an interior material, possibly porous (pore system 2), retained within the macropores. The characterizing feature of the matrix is a continuous free volume between the interior material and the inner pore walls of the macropores. The support matrices can be in a packed or fluidised bed format or in the form of a monolithic plug. In the preferred variants the continuous free volume permits liquid flow through the matrix, preferably between two opposite ends of the matrix. The dimensions of the continuous free volume are typically selected such that at least 1%, such as at least 4%, of the liquid will pass through the matrix in the continuous free volume. For a matrix in form of a monolithic plug this means 100% liquid flow through the matrix.
Pore Systems
The sizes of the macropores of the empty base matrix without interior material are typically in the interval 0.1-1000 &mgr;m, such as 0.5-1000 &mgr;m, with preference for 1-100 &mgr;m (pore system 1). The base matrix may also contain a set of less pores (pore system 3) having pores in the interval 10 Å-0.5 &mgr;m, such as 10 Å-0.1 &mgr;m.
The upper limit of the pore sizes (pore system 2) depends on the pore sizes of pore system 1. In case the pores of pore system 1 are sufficiently large, pore system 2 may contain interior material that may or may not be macroporous (pore system 4). Pore system 2 is in the preferred variants microporous, i.e. its pore sizes are ≦0.5 &mgr;m, such as ≦0.1 &mgr;m. In case pore systems 2 and 4 are macroporous, they can be considered being a part of pore system 1.
The free volume present in the inventive matrices will increase the convective surface area. This will mean faster mass transport and increased break through capacity for interactions with solutes in a through-flowing liquid. The convective surface area of a matrix according to the invention will typically be at least 25%, such as at least 50% or at least 75%, higher than the convective surface of the base matrix without interior material.
The preferred pore systems consist of a three dimensional network of pores, which network comprises a number of pores, pore branches, pore bifurcations etc., and in the preferred variants also cavities communicating with each other via the pores. This applies to macropore systems, including convective pore systems, as well as micropore systems.
In the preferred base matrices, the macropore system is built up of cavities in the form of spheres with connecting pores between the spheres. The diameters of the spheres may be between 1 &mgr;m-100 &mgr;m, such as 1 &mgr;m-25 &mgr;m. The diameters of the connecting pores are normally about {fraction (1/10)}-⅓ of the diameters of the spheres, for instance between 0.1 &mgr;m-10 &mgr;m, such as 0.5 &mgr;m-10 &mgr;m. In case the matrices are in form of beads/particles, the cavities typically have diameters of <{fraction (1/9)} of the diameter of the particles.
In some preferred.variants the interior material has a size and/or form prohibiting it to leave the base matrix, i.e. is a so called “jailed interior material”.
Base Matrices
Base matrices having pore systems built up by spherical cavities with connecting pores between the cavities )are readily available from the prior art. See for instance U.S. Pat. No. 5,833,861 (PerSeptive Biosystems), EP 288,310 (Unilever), EP 68310 (Unilever), WO 9719347 (Amersham Pharmacia Biotech AB), U.S. Pat. No. 5,334,310 (Cornell Research Foundation), WO 9319115 (Amersham Pharmacia Biotech AB) etc.
The base matrices may in principle be based on materials that in the field are per se known for the manufacture of chromatographic adsorbents in form of monolithic plugs or particles. Thus the main constituent in the base matrix can god be based on organic polymers, such as native polymers (so called biopolymers) and synthetic polymers, and inorganic material. The interior material is primarily based on organic polymers that may be native or synthetic.
Illustrative examples of biopolymers are polysaccharides such as dextran, agarose, cellulose, ca

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